1. Field of the Invention
The present invention relates to a zoom lens barrel which permits zooming by both a straightforward operation along the optical axis and a rotating operation about the optical axis.
2. Description of the Prior Art
The known zoom lens barrel is either of a straightforward operation type, or a rotating operation type. The former type drives the movable optical component of a zoom lens when a zoom operating member is moved along the optical axis. This type of zoom lens barrel is capable of prompt operation from the nature of its operational direction. However, it is not suitable for fine control. In addition, a single operating member is used in this type of zoom lens barrel for both zooming and focusing. It is often constructed such that it is moved straightforward for zooming and rotated for focusing. In this case, both operations can be carried out simultaneously and promptly, but it is difficult for zooming alone to be performed with a focusing condition kept unchanged. Meanwhile, the rotating operation type of zoom lens barrel makes fine control possible through fine movements of an operational member. In addition, an operating member is normally independent of a focusing operating member, thereby permitting zooming alone with a focusing condition kept unchanged. In this case, however, prompt operation is not possible.
Disclosed by Japanese Utility Model Publication No. 49-18027 is a zoom lens barrel which obviates the disadvantages of a both operation system and which is selectively and alternatively capable of a straightforward zoom operation and a rotating zoom operation. The zoom lens barrel disclosed in this publication requires guide cam members for alternatively controlling the straightforward zoom operation and rotating zoom operation, in addition to a cam for use in zooming. Furthermore, it requires a changeover means for selection of such operations, and as a result, an operation set by the changeover means is only possible and a mechanism for operation selection is also complex.